用Python嵌套导入声明是不是不好?

不,不是。见 PEP8 python styling standards 。以下是相关摘录:

Imports

- Imports should usually be on separate lines, e.g.:

    Yes: import os
         import sys

    No:  import sys, os

  it's okay to say this though:

    from subprocess import Popen, PIPE

- Imports are always put at the top of the file, just after any module
  comments and docstrings, and before module globals and constants.

  Imports should be grouped in the following order:

  1. standard library imports
  2. related third party imports
  3. local application/library specific imports

这不是嵌套,只是导入特定的名称。这本身没什么问题,但还是一如既往地咨询 PEP 8 样式指南。

我会避免的。sdolan引用的PEP 8中给出的示例是从模块内部导入特定名称,但您要问的是在一行中导入多个不同的包。它不会中断,但是将它分离出来会更整洁,并且使以后重构和更改导入更容易。